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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The lack of a satisfactory method for long-term preservation of hearts during transport limits the source of human hearts for transplant to the geographic vicinity of the transplant center. Experimentally, reduction of myocardial oxygen requirements with hypothermia and cardioplegia prolong storage time to 48 h, but always with some evidence of myocardial damage. In this study, the combination of hypothermia with a procedure known to increase oxygen tension in cardiac muscle, gas perfusion, preserved contractile activity in guinea pig hearts for 24 h and did not cause edema. Cardioplegia or gas perfusion at temperatures below 10 degrees C or above 20 degrees C resulted in failure of hearts to contract upon rewarming. Contracture, dehydration, elevation of tissue calcium, reduced perfusate flow, and elevated creatine kinase levels occurred if liquid reperfusion was begun at 15 degrees C but not 25 degrees C. The results suggest that under the appropriate conditions, hypothermic gas perfusion is a potentially useful means of extending storage time of hearts for transplant.
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PMID:Preservation of guinea pig hearts by hypothermic gas perfusion. 250 68

In the early 1970's, calcium ions were implicated in the mechanism underlying the perturbation of the "set point" for body temperature produced by a thermolytic drug. Since Ca++ is thought to be involved in the incapacitating effects of ethanol on body temperature and motor coordination, this investigation sought to compare the differential central actions of a Ca++ chelating agent with those of a Ca++ channel antagonist on ethanol-induced poikilothermia and motor functions. A chronically indwelling cannula for intracerebroventricular (ICV) injection was implanted stereotaxically in each of 25 adult male Sprague-Dawley rats. Following postoperative recovery, each rat was given ethanol in a 20% v/v solution by the intraperitoneal route in a dose of 4.0 g/kg, which was selected to insure a clear-cut impairment of autonomic and motorial functions. Colonic temperature, behavioral sleep, righting reflex and degree of motor coordination on a rotorod were monitored at selected intervals for 5.0-7.0 hr after the injection of ethanol. Two experimental designs were used: First, either 12.5, 25 or 50 micrograms ethyleneglycol-bis-(beta-amino ethyl ether) N,N'-tetra-acetic acid (EGTA), or 25 or 50 micrograms verapamil, both dissolved in an artificial CSF vehicle, were infused ICV at the same time as ethanol's administration. In the second design, the compounds were infused at the nadir of the ethanol-induced temperature decline. EGTA infused ICV in the rat together with ethanol produced a dose-dependent inhibition of ethanol hypothermia and a more rapid recovery of the animal's righting reflex, arousal and motor coordination than that following ethanol alone. Although verapamil infused ICV in the 50 micrograms but not 25 micrograms dose minimized the poikilothermic response to ethanol, it was not as efficacious as that of EGTA. When infused ICV at the point of maximum fall in the rats' temperature. EGTA entirely reversed the hypothermia induced by ethanol and evoked a thermogenic response in the rat. In contrast, verapamil infused ICV in the same doses tended only to retard the further decline in the animal's body temperature. Similarly EGTA was far more effective than verapamil in ameliorating the other physiological actions of ethanol in terms of the reversal of areflexia, behavioral sleep and motor incoordination. These results suggest that the characteristic attributes of membrane Ca++ in terms of its binding and other neuronal properties play a significant functional role in the incapacitating action of ethanol on the diverse physiological processes mediated by the brain.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Alcohol-induced poikilothermia, sleep and motor impairment: actions on brain of EGTA and verapamil. 251 53

Ca2+-tolerant ventricular myocytes from adult rats were electrically stimulated. The maximal contraction frequency (fm) was determined at different temperatures. In drug-free Tyrode solution, fm follows the Arrhenius equation from 7 to 39.5 degrees C. However, verapamil introduces a discontinuity around 27 degrees C into the Arrhenius plot of fm. Above this transition temperature the calcium antagonist lowers fm more pronouncedly than below. Below, a tenfold higher concentration is needed for the same relative effect as at 37 degrees C. It is argued that this finding might be important in cardiac surgery when calcium antagonists are used for cardioplegia at deep hypothermia.
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PMID:Temperature dependence of verapamil action. 258 45

We have previously demonstrated resiniferatoxin (RTX) to be an ultrapotent analog of capsaicin. Like capsaicin, RTX initially induces neurogenic inflammation, pain, and hypothermia and then causes desensitization of these responses. We examine here the duration of desensitization following acute treatment with the maximal tolerated dose of RTX. Desensitization to neurogenic inflammation began to diminish by 7 days, whereas desensitization to pain and to induction of hypothermia persisted for several weeks. Interestingly, a partial hypothermic response returned within 24 h if challenge was with RTX at 500-fold its ED50 for control animals; the animals, moreover, maintained their ability to thermoregulate in a hot environment. The time course of the morphological changes--ultrastructure and calcium staining--of dorsal root ganglion neurons was examined in parallel. The ultrastructural changes were evident by 4 h and persisted for the duration of the experiments. Limited calcium staining was visible at 12 and 24 h after treatment but then diminished. In comparison with capsaicin treatment, RTX caused more long-lasting desensitization as well as a distinct spectrum of response.
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PMID:Duration of desensitization and ultrastructural changes in dorsal root ganglia in rats treated with resiniferatoxin, an ultrapotent capsaicin analog. 261 60

The effects of indeloxazine hydrochloride [(+/-)-2-[(inden-7-yloxy)methyl]morpholine hydrochloride, YM-08054], a new cerebral metabolic enhancer, on learned behavior and central monoaminergic function were compared to those of other cerebral metabolic enhancers in animals. Indeloxazine enhanced passive learned behaviour in rats and ameliorated cerebral ischemia-induced learned disturbances in gerbils. Reserpine-induced hypothermia in mice, ponto-genicullo-occipital (PGO) waves in reserpinized cats and caudate spindle activity in cats were reduced by the administration of indeloxazine, suggesting that the drug possesses facilitatory effects on central monoaminergic systems. In contrast, piracetam, calcium-hopantenate, idebenone and bifemelane had no significant effect on learned behavior or central monoaminergic function, with the exception of bifemelane which antagonized reserpine-induced hypothermia. These results are in contrast to the findings that all tested cerebral metabolic enhancers, including indeloxazine, prolonged the survival time of mice subjected to anoxia. The greater effect of indeloxazine to other cerebral metabolic enhancers, in facilitating learned behavior, may be attributable to its broader effects on central monoaminergic systems.
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PMID:Pharmacological effects of indeloxazine, a new cerebral activator, on brain functions distinct from other cerebral metabolic enhancers. 261 13

Calcium plays an essential role in ischemic events observed during cardiac surgery. Many experiments have studied the effects of calcium channel blockers on intracellular calcium overload during the periods of cardiac ischemia and reperfusion. Calcium channel blockers are no longer used before and during cardiac surgery because hypothermia inhibits their pharmacological action. However, during the post-operative period, calcium channel blockers are the drugs of choice to control coronary spasm, and arterial hypertension which is secondary to peripheral vasoconstriction.
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PMID:[Role of calcium blockers in protecting the myocardium in cardiac surgery]. 267 78

The effect of two Ca2+ channel inhibitors (CCIs) on ethanol-induced hypothermia and hypnosis, on tolerance formation to both effects, and on audiogenic convulsions during ethanol withdrawal was studied in rats. Nifedipine, 2 and 5 mg/kg IP, significantly augmented the hypnotic action of ethanol without affecting hypothermia. Diltiazem failed to influence either effect of the toxin. Rectal temperature did not change in ethanol-naive rats after acute injection of diltiazem or nifedipine. Both drugs dose-dependently suppressed the development of tolerance to the hypothermic effect of ethanol without affecting the tolerance to the hypnotic action. Only nifedipine markedly suppressed the audiogenic seizure response in ethanol withdrawn animals. These data suggest that Ca2+ channels play a role in both acute and chronic effects of ethanol while pointing to certain differences in behavioral effects of various CCIs.
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PMID:Different effect of diltiazem and nifedipine on some central actions of ethanol in the rat. 271 89

We studied the effects of the electrolyte composition (K, Ca, Na, Mg) and the temperature of the extracellular fluid on the tension development of isolated canine coronary arterial strips. In 20 mEq/l K solution, the calcium produced a dose-dependent contraction at concentrations higher than 0.2 mEq/l. This Ca-induced contraction was strongly inhibited by hypothermia below 20 degrees C and also by 30 mEq/l magnesium. In the presence of 20 mEq/l K, the reduction of sodium concentrations to less than 90 mEq/l increased the tension which was inversely related to the concentration. Cooling below 25 degrees C of this solution or addition of 20 mEq/l magnesium to low-Na solution markedly reduced contractions. It is concluded that the electrolyte containing K20, Ca0.1, Na110 and Mg30mEq/l or cooling below 20 degrees C can maintain relaxation in the dog coronary artery.
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PMID:[Effects of electrolyte composition and temperature of extra-cellular fluid on coronary artery contraction]. 274 12

This study investigates whether the addition of magnesium to a hyperkalemic cardioplegic solution containing 0.1 mM ionized calcium improves myocardial preservation, and whether there is an optimal magnesium concentration in this solution. Isolated perfused rat hearts were arrested for two hours by this cardioplegic solution, which was fully oxygenated and infused at 8 degrees C every 15 minutes to simulate clinical conditions. The cardioplegic solution contained either 0, 2, 4, 8, 16, or 32 mM magnesium. At end-arrest, the myocardial creatine phosphate concentration (nanomoles per milligram of dry weight) was 20.7 +/- 2.1, 22.9 +/- 1.7, 24.8 +/- 2.0, 31.3 +/- 1.4, 33.1 +/- 1.8, and 31.6 +/- 0.8, respectively, in hearts given cardioplegic solution containing these magnesium concentrations. Thus, the concentration of creatine phosphate was significantly higher at end-arrest when the cardioplegic solution contained 8, 16, or 32 mM than 0 or 2 mM magnesium (p less than 0.002) or 4 mM magnesium (p less than 0.02), and highest with 16 mM magnesium. Also, creatine phosphate was more sensitive to the magnesium concentration of the cardioplegic solution than was end-arrest adenosine triphosphate levels, which did not differ among the experimental groups. Aortic flow, expressed as a percentage of prearrest aortic flow, was 60.3 +/- 5.0, 70.2 +/- 5.5, 71.6 +/- 4.4, 71.8 +/- 4.8, 81.0 +/- 5.0, and 71.8 +/- 5.3, respectively. The addition of magnesium to the cardioplegic solution improved recovery of aortic flow (p less than 0.05, 16 mM versus 0 mM magnesium). We conclude from these data that with deep myocardial hypothermia and at an ionized calcium concentration of 0.1 mM, the addition of magnesium, over a broad concentration range, improved preservation of myocardial creatine phosphate and, at a concentration of 16 mM, improved aortic flow. The optimal magnesium concentration in the cardioplegic solution was 16 mM.
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PMID:Myocardial preservation related to magnesium content of hyperkalemic cardioplegic solutions at 8 degrees C. 275 48

A 9-year-old girl was admitted with hypertension and severe congestive heart failure. Upon physical examination, a discrepancy of blood pressure between arm and leg was noted. Aortography revealed narrowing about 5 cm in length at the midportion of the descending thoracic aorta. Bypass operation of the narrow segment was performed under mild hypothermia with the diagnosis of atypical coarctation of the aorta. It was supposed that the patient might outgrow the graft and the graft would become too small for grown-up patient in diameter and length, then the haemodynamics would become less satisfactory and too much tension on the suture line would occur. A woven Dacron graft, 10 mm in diameter, 15 cm in length, was anastomosed proximally and distally to the coarcted segment at a distance of about 6 cm. So, the graft was disposed in a C-shaped configuration. It was expected that the arch of the graft would open more widely with increase of her stature, even if the graft does not increase in length. She has been followed for twelve years. Hypertension of upper extremity and arm-to-leg gradients of the systolic blood pressure were recognized from two years after the operation, particularly with exercise. However, cardiomegaly and left ventricular hypertrophy in ECG were improved. She appears to have been developing normally with no cardiac symptoms. Estimating from angiography, the distance between proximal and distal anastomoses stretched about 2 cm during the period of rapid growth, though calcification of the graft had been seen from four years after the operation, perhaps due to increased calcium turnover in childhood.
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PMID:[Bypass operation adaptable to stature increase in child with atypical coarctation of the aorta]. 277 55


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